Effects of sedentary behavior in Metabolic Syndrome and its components in adults: A Systematic Review

Introduction: the current society has been involved in activities that require less energy expenditure, this type of activity that requires energy expenditure <1.5 METs, excluding sleep, is called sedentary behavior and is independently associated with physical a ctivity to deleterious health factors , as metabolic syndrome. Objective: to investigate, through a systematic review, the effects of sedentary behavior on the metabolic syndrome and its components in adults. Methodology: This is a systematic review, using the Trip Database databases through the following descriptors: adults; sedentary behavior or screen time or sedentary life style; cardiometabolic risk or cardiovascular risk or metabolic risk score, published between 2013 and 2018. Results: Some cross-sectional studies show a greater chance of developing metabolic syndrome when sedentary time is increased. However, most sedentary time intervention studies with mild physical activity or posture change do not have a significant effect on cardiometabolic mark ers. Conclusion: According to the results of the selected studies, there is an association between high sedentary time and the development of metabolic syndrome and its components in adults Keywords— Adult, Sedentary Behavior, Metabolic Syndrome.


I. INTRODUCTION
The current model of society and technological advances can negatively affect the population's way of life, causing the human being to have to work less physically to perform his or her daily life tasks. For this reason, sitting time (watching televis ion, motorized, using the computer, playing video games, hanging around chatting with friends, talking on the phone among other similar activities) who require little energy expenditure, has become increasingly prevalent society current (CHURCH et al., 2011). In this context, the definition of sedentary behavior was defined as a series of states in which the individual remains awake with energy expenditure <1.5 METs (Metabolic Equivalent Term), excluding sleep time (TREMBLA Y et al., 2017).
Farias Júnior (2011) describes in his study that the term sedentary behavior is different from the sedentary one within the level of physical activity, since it has specific "categorical" as well as pathological consequences in the health of the individuals. Sedentary behavior is not characterized simply as an absence of physical activities or the attendance of specific scores in its classification (BIDDLE et al., 2009).
Sedentary behavior has been associated with several deleterious health factors such as obesity, type 2 diabetes, cardiovascular diseases and all-cause mortality (YOUNG et al., 2016). Among these factors, the metabolic syndrome has also received differentiated attention, since it is considered as a group of factors, which allies increase the chance of developing type 2 diabetes and cardiovascular disease (HUANG, 2009). Metabolic syndrome is classified in several ways, but the definition of the National Cholesterol Education Program (NCEP) is one of the most widely used criteria for the definition of metabolic syndrome, since it encompasses its main characteristics: hyperglycemia / insulin resistance, visceral obesity, atherogenic dyslipidemia and hypertension in addition to using measurements and laboratory results readily available to physicians, facilitating their clinical and epidemiological application (PENALVA, 2008).
The definition of the NCEP ATP III states that the individual is diagnosed with the metabolic syndrome when he has at least three of the following five criteria: waist circumference ≥102 cm for men and ≥88 cm for woman, blood pressure above 130/85 mmHg, fasting triglycerides (TG) above 150 mg / dL, fasting high density lipoprotein (HDL) levels below 40 mg / dl (men) or 50 mg / dl (women), and fasting blood glucose above 100 mg / dl (GRUNDY et al, 2005).
Some research, such as Young et al. (2016), demonstrate an increased chance of developing metabolic syndrome associated with increased sedentary time.
However, these data are not conclusive, mainly in quantitative terms to affirm how much and how to reduce the sedentary time, for health benefits, especially the reduction of the risk of developing metabolic syndrome. In this context the objective of this systematic review is to investigate the effects of sedentary behavior on the metabolic syndrome and its components in adults.
II. METHODOLOGY It is a systematic review of the literature, which is a way of synthesizing the information available at a given moment, on a specific problem, in an objective and reproducible way, by means of a scientific method (BANNINGAN; DROOGAN, ENTWISTLE, 1997). The stages of the research were divided into: theme definition, issue study problem, search strategy, inclusion and exclusion criteria, evaluation of included studies and synthesis of data collected.

Defining the problem of the study question
The question for the study was formulated from the PICO strategy, which according to Santos and Nobre (2007) means an acronym for Patient (population), Intervention, Comparison and Outcomes.

Search strategy
The search for studies was carried out in the database "TRIP Database" through the PICO strategy, in which the descriptors used were: P: adults; I: sedentary behavior or screen time or sedentary life style; C: has not been applied; O: cardiometabolic risk or cardiovascular risk or metabolic risk score or metabolic syndrome.
The choice of the TRIP Database search tool was based on the fact that it is a free clinical search engine whose primary function is to help physicians and healthcare professionals identify the best scientific evidence available to answer clinical questions. Its roots are firmly in the world of health research, based on scientific evidence.

Inclusion and exclusion criteria
Included in this review were primary cross -sectional, longitudinal, cohort, and intervention studies that were published in English between 2013 and 2018 and evaluated the influence of sedentary behavior, measured by questionnaire or objectively, on the metabolic syndrome and its components in adults.
We excluded from this review articles that do not fit the inclusion criteria, studies that evaluate the population with locomotor and functional limitations and / or individuals with neurodegenerative diseases in general.

III. RESULTS
The search strategy allowed to find 19258 articles, after the application of the inclusion and exclusion criteria, the researches were allocated as shown in Figure 1   The association with TV was diluted, but remained highly significant after adjustments with all measured covariates, including several potentially obesogenic food items associated with TV viewing. The intakes of food items such as sausage, beer and soft drinks were directly associated with TV viewing, while the intakes of oat and barley, fish, and fruits and berries were associated indirectly. After these adjustments, non-TV sedentary behaviour remained associated with adiposity indices only in women.  The within-group analysis provides preliminary evidence that exercising and reducing ST may result in improvements in metabolic biomarkers that are not seen with exercise alone, though betweengroup differences did not reach statistical significance. The sample consisted of 09 overweight or obese adults (body mass index, 28.7 ± 2.7 kg, m (-2) adults (30 ± 15 years)) SBP during Standing (132 ± 17 mmHg), WALK (133 ± 17 mmHg) and CYCLE (130 ± 16 mmHg) were lower in comparison with SIT (137 ± 17 mmHg) (all P <0.01). CYCLE was smaller than STANDING (P = 0.04) and WALKING (P <0.01). For DBP, only CYCLE (69 ± 12 mmHg) was lower than SIT (71 ± 13 mmHg; P <0.01). Compared with SIT, WALK, STANDING and CYCLE, reduced SBP load by 4%, 4% and 13%, respectively (all P <0.01) Evaluation of sit-stand workstations in an office setting: a randomised controlled trial IV. DISCUSSION In this review, as shown in Table 2, most of the studies were interventional, and they evaluated changes in sedentary behavior to measure changes only in the components of the metabolic syndrome. Only 03 articles, transversal, all objectively measured, directly correlated metabolic syndrome with sedentary behavior.
These studies, which directly correlated metabolic syndrome with sedentary behavior, show a positive relationship between these variables, (SALEH; JANSSEN, 2014) showed this association even after controlling for confounding factors (odds ratio (OR) = 1.60) and (KING et al., 2016) also states that sedentary time was independently associated with a higher chance of metabolic syndrome (OR = 1.12). These data corroborate with that of other review studies, which also show this same increased chance (YOUNG et al., 2016).
One research found no association between increased sedentary time and chance of developing metabolic syndrome when controlled confounding factors Regarding the components of the metabolic syndrome (glycemia, fasting HDL and triglycerides, blood pressure and waist circumference), it is also shown in the cross-sectional studies of this research, the chance of developing deleterious health outcomes when sedentary behavior is elevated. However, when researches that involved some intervention on the sedentary time-off are taken into account, only two studies showed a significant post-intervention difference (ZEIGLER et al., 2016; PUIG-RIBERA et al., 2015). These data are similar to those of the review by (DE REZENDE, 2014), where the authors state that there is insufficient evidence to confirm an association between individual cardiovascular risk factors and metabolic syndrome.

V.
CONCLUSION It is concluded, after analysis of the studies, that there is an association between high sedentary time and the development of metabolic syndrome, however, most intervention studies do not show a significant change in cardiometabolic components when sedentary time breaks with mild physical activity. Much of these non-significant results in the intervention studies cited in this review may be due to acute effect studies or rapid interventions.
For this reason, it is necessary that more longitudinal studies be developed to investigate the chronic effect of these interventions, the number of breaks in the sedentary time, and the necessary duration of the same, in order to have significant effects on the improvement of the cardiometábolic components